Extraction method for separating uranium, plutonium, and fission products from compositions containing same

摘要

834,529. Separation of plutonium. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. March 11, 1944 [April 3, 1943], No. 4577/44. Class 39(4). Plutonium is separated from an aqueous nitric acid solution of neutron-irradiated uranium, in which the plutonium is in its fluoride-insoluble (plutonous) state, by extraction with an organic solvent which extracts uranyl nitrate, leaving plutonous nitrate and fission products in the aqueous phase. The aqueous phase may then be oxidised and contacted again with the solvent which extracts both plutonium and any remaining uranium, most of the fission products again remaining in the aqueous phase. Agitation of this extract with water containing a reducing agent causes plutonium to pass into the water layer from which it may be precipitated, e.g. as fluoride, iodate, or hydroxide. Alternatively a reducing agent may be added to the solvent extract to precipitate the plutonium. The preferred solvent is diethyl ether, but others referred to are methyl ethyl ether, isopropyl ether, methyl ethyl ketone, nitropropane, nitrobutane, and a mixture of acetone and xylene. Suitable oxidising agents are listed, examples being sodium dichromate and chlorine. The reducing agent may be sulphur dioxide or hydrogen peroxide. To assist the extractions, soluble salts, for example lithium nitrate or aluminium nitrate, may be added to the aqueous solution. The Specification as open to inspection under Sect. 91 describes also the extraction with ether of an initial solution in which the plutonium is in the oxidised state ; both plutonium and uranium pass into the solvent layer which is shaken with water containing sulphur dioxide as a reducing agent to separate plutonium. This subject-matter does not appear in the Specification as accepted.